On 15Sep2023 10:49, scruel tao <scru...@hotmail.com> wrote:
```python
class A:
... def __init__(self):
... pass
...
```
On many books and even the official documents, it seems that many authors prefer to call `__init__`
as a "method" rather than a "function".
The book PYTHON CRASH COURSE mentioned that "A function that’s part of a class is a
method.", however, ` A.__init__` tells that `__init__` is a function...
As mentioned, methods in Python _are_ functions for use with a class.
A.__init__
<function A.__init__ at 0x0000026CFC5CCEE0>
a = A()
a.__init__
<bound method A.__init__ of <__main__.A object at 0x0000026CFC1BB400>>
I wonder how can I call `__init__` as? Consider the output above.
Maybe both are OK?
As you can see, they're both legal expressions.
The thing about `__init__` is that it's usually called automatically
which you make a new object. Try putting a `print()` call in your
`__init__` method, then make a new instance of `A`.
The purpose of `__init__` is to initialise the object's attribute/state
after the basic, empty-ish, object is made.
Like other dunder methods (methods named with double underscores front
and back) it is called automatically for you. In a subclass the
`__init__` method calls the subperclass `__init__` and then does
whatever additional things might be wanted by the subclass.
Let's look at what you used above:
>>> A.__init__
<function A.__init__ at 0x0000026CFC5CCEE0>
Here's we've just got a reference to the function you supposlied with
the class definition for class `A`.
This:
>>> a = A()
>>> a.__init__
<bound method A.__init__ of <__main__.A object at 0x0000026CFC1BB400>
Here's you've accessed the name `__init__` via an existing instance of
`A`, your variable `a`. At this point you haven't called it. So you've
got a callable thing which is a binding of the function to the object
`a` i.e. when you call it, the "bound method" knows that t is associated
with `a` and puts that in as the first argument (usually named `self`).
Cheers,
Cameron Simpson <c...@cskk.id.au>
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